U.S. patent number 7,681,558 [Application Number 12/014,312] was granted by the patent office on 2010-03-23 for system and method to control fuel vaporization.
This patent grant is currently assigned to Ford Global Technologies, LLC. Invention is credited to Larry Dean Elie, Allan Roy Gale, Paul Raymund Nicastri, Ross Dykstra Pursifull, Joseph Norman Ulrey.
United States Patent |
7,681,558 |
Gale , et al. |
March 23, 2010 |
System and method to control fuel vaporization
Abstract
A method for improving fuel heating is presented. The method can
reduce system complexity and cost when fuel is heated within a fuel
injector. In one embodiment, the method independently heats and
injects fuel by changing the direction of current flow through a
fuel circuit.
Inventors: |
Gale; Allan Roy (Livonia,
MI), Ulrey; Joseph Norman (Dearborn, MI), Elie; Larry
Dean (Ypsilanti, MI), Nicastri; Paul Raymund (Plymouth,
MI), Pursifull; Ross Dykstra (Dearborn, MI) |
Assignee: |
Ford Global Technologies, LLC
(Dearborn, MI)
|
Family
ID: |
40849598 |
Appl.
No.: |
12/014,312 |
Filed: |
January 15, 2008 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20090178651 A1 |
Jul 16, 2009 |
|
Current U.S.
Class: |
123/557; 239/135;
123/549; 123/490 |
Current CPC
Class: |
F02D
41/0025 (20130101); F02M 31/125 (20130101); F02M
53/06 (20130101); F02D 41/20 (20130101); F02D
2041/2058 (20130101); F02M 51/0603 (20130101); F02D
19/0655 (20130101); F02D 2200/0606 (20130101); F02M
69/045 (20130101); Y02T 10/126 (20130101); F02D
2041/2048 (20130101); F02M 51/0671 (20130101); F02M
69/044 (20130101); Y02T 10/12 (20130101); F02D
2200/0611 (20130101); Y02T 10/36 (20130101); Y02T
10/30 (20130101) |
Current International
Class: |
F02G
5/00 (20060101) |
Field of
Search: |
;123/549,557,490
;239/135 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
US. Appl. No. 11/566,890, filed Dec. 5, 2006, Wineland et al. cited
by other .
U.S. Appl. No. 11/566,932, filed Dec. 5, 2006, Stephan et al. cited
by other .
U.S. Appl. No. 11/566,911, filed Dec. 5, 2006, Gale et al. cited by
other .
U.S. Appl. No. 11/566,981, filed Dec. 5, 2006, Maranville et al.
cited by other .
U.S. Appl. No. 11/566,966, filed Dec. 5, 2006, Gale et al. cited by
other.
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Primary Examiner: Cronin; Stephen K
Assistant Examiner: Bacon; Anthony L
Attorney, Agent or Firm: Lippa; Allan J. Alleman Hall McCoy
Russell & Tuttle LLP
Claims
The invention claimed is:
1. A fuel injector for heating and injecting fuel into an internal
combustion engine, said fuel injector comprising: an element to
control flow of fuel through said fuel injector; a heating element
to heat fuel passing through said fuel injector, said heating
element separate from said element that controls fuel flow through
said fuel injector; and a circuit comprising said heating element
and said element that controls fuel flow through said fuel
injector, said circuit heating fuel passing through said fuel
injector without actuating said fuel injector when current flows in
a first direction and is below a predetermined level, said circuit
heating fuel passing through said fuel injector and actuating said
fuel injector when current flows in said first direction and is
above said predetermined level, and said circuit actuating said
fuel injector without substantially heating said fuel injector when
current flows to said fuel injector in a second direction, said
second direction different from said first direction, wherein said
actuating of said fuel injector delivers fuel from the fuel
injector.
2. The fuel injector of claim 1 wherein said element to control
fuel flow is a coil or a piezoelectric device.
3. The fuel injector of claim 1 wherein said fuel injector has an
electrical connector with two pins. has two pins.
4. The fuel injector of claim 2 wherein said coil is used to move a
spool valve or an injector armature pintle, and wherein there is a
current flow control device in series with said heating element and
wherein there is no current flow control device in series with said
element to control flow of fuel through said fuel injector.
5. The fuel injector of claim 1 wherein said fuel injector is
designed to inject fuel directly into a cylinder.
6. The fuel injector of claim 1 wherein said fuel injector is
designed to inject fuel into an intake port leading to a
cylinder.
7. The fuel injector of claim 1 wherein said fuel injector is
designed to inject a fuel comprising at least one of: gasoline,
propane, ethanol, diesel, bio-diesel, butenol, proponol, kerosene,
or jet fuel.
8. The fuel injector of claim 1 wherein said fuel injector accepts
current from a single bi-directional current source.
9. The fuel injector of claim 1 wherein said circuit is further
comprised of one or more devices that limit flow of said current
depending on the direction of said current.
10. The fuel injector of claim 9 wherein said device that limits
flow of current is a diode.
11. A method to operate a fuel injector, the method comprising:
supplying a first current in a first direction to heat fuel passing
through said fuel injector without actuating said fuel injector
when said first current is below a predetermined level, said first
current heating fuel passing through said fuel injector and
actuating said fuel injector when said current is above a
predetermined level, said first current delivered at predetermined
crankshaft intervals; and supplying a second current in a second
direction, said second direction different from said first
direction, to actuate said fuel injector without substantially
heating said injector, fuel flowing through said fuel injector
while current is supplied in said second direction.
12. The method of claim 11 wherein said first current and said
second current are supplied from a common source.
13. The method of claim 12 wherein said first current and said
second current are routed through a pair of wires.
14. The method of claim 11 wherein said first current is supplied
in said first direction for a predetermined period of time when an
engine that said fuel injector is injecting fuel to is started.
15. The method of claim 11 wherein said first current is supplied
by an H-bridge circuit.
16. The method of claim 11 wherein said second current is supplied
in said second direction in excess of an amount necessary to permit
fuel flow through said fuel injector.
17. The method of claim 11 wherein said first current is supplied
in said first direction when an engine is not rotating, and wherein
said current is supplied in said second direction when said engine
is rotating.
18. A system for heating fuel supplied to an engine, comprising: a
plurality of fuel injectors, each fuel injector of said plurality
of fuel injectors comprising a flow control element, a heating
element separate from said flow control element, and a circuit
comprising said heating element and said element that controls fuel
without actuating said fuel injector when current is in a first
direction and below a predetermined level, said circuit heating
fuel passing through said fuel injector and actuating said furl
injector when current is in said first direction and above said
predetermined level, and said circuit actuating said fuel injector
without substantially heating said fuel injector when current flows
to said fuel injector in a second direction, said second direction
different from said first direction, wherein said actuating of said
fuel injector delivers fuel from the fuel injector; and a current
supply comprised of a single switch that switches, between two
current sources, a first terminal of each fuel injector that
comprise said plurality of fuel injectors, said current supply also
comprised of a plurality or switches configured to switch a second
terminal of each of said plurality of fuel injectors between said
two current sources.
Description
FIELD
The present description relates to a system and method for heating
fuel and controlling fuel injection of a fuel injector that
operates as part of an internal combustion engine.
BACKGROUND
Fuel vaporization tends to decrease as ambient temperature
decreases. This can make engine starting more difficult at lower
temperatures because reduced fuel vaporization can result in an
air-fuel mixture near the engine's spark plug that is less than the
fuel's lower flammability limit. Further, lower rates of fuel
vaporization may make engine starting particularly difficult for
certain types of fuels (e.g., ethanol). One example way to improve
fuel vaporization is described in U.S. Patent Application
2005/0263136. This patent application describes placing a heating
coil around the nozzle of a port fuel injector. The heating coil is
supplied electrical energy through an electrical connector that
attaches to an engine wiring harness. Heat produced by the heating
coil is conducted through the injector to heat fuel that resides
within the injector. This heating apparatus purportedly improves
fuel vaporization.
The above-mentioned system can also have several disadvantages.
Namely, the system heats the injector through conducting heat from
a source outside the injector body. Since the heat source is
external to the injector, some energy intended to heat the injector
is lost to heating the engine and may therefore be less efficient
than is desired. In addition, the heating device requires an
additional electrical connector to route power to the heating
device. An additional connector increases the number of wires and
connections. Therefore, system reliability may be reduced when such
a system is used to increase the temperature of fuel injected to an
engine. In addition, the system may be difficult to implement on
direct injection engine because there may be less space available
to place a heating coil around the injector nozzle.
The inventors herein have recognized the above-mentioned
disadvantages and have developed a method that offers substantial
improvements.
SUMMARY
One embodiment of the present description includes a system to heat
and inject fuel to an internal combustion engine, the system
comprising: an internal combustion engine; a fuel injector capable
of delivering fuel to said internal combustion engine, said fuel
injector comprising a heating element and a fuel flow control
element; and a controller that supplies current to said fuel
injector in a first direction to heat fuel that flows through said
fuel injector, and said controller supplying current to said fuel
injector in a second direction to deliver fuel to said engine
without substantially heating the fuel delivered through said fuel
injector. This method overcomes at least some disadvantages of the
above-mentioned method.
Fuel vaporization and system reliability can be improved by a
system that heats fuel from within the fuel injector and that
supplies fuel heating energy through the same conductors that are
used to actuate the injector. In one embodiment, a system provides
current in a first direction to heat fuel contained or passing
through the fuel injector, and the system actuates the fuel
injector by providing current in a second direction. In other
words, the system controls injector heating and actuation (opening
and/or closing) by controlling the direction that current is
delivered to the fuel injector. This allows the system to use a
single pair of wires to actuate the injector and heat fuel passing
through the injector. Consequently, fewer conductors have to be
provided, less electrical connections are made, and existing fuel
injector connectors can be used to realize the system. Furthermore,
the fuel heating and fuel injection elements can be integrated into
a small package.
The present description can provide several advantages.
Specifically, the approach can improve system reliability, reduce
the cost of heating fuel, and it can be implemented with few
changes to existing fuel systems. The system can also be used on a
variety of injector designs. For example, the described system can
be used to heat fuel flowing through port style injectors,
injectors that inject fuel directly into a cylinder, injectors
having a single coil controlled pintle, and injectors that use dual
coil spool valve operated injectors.
The above advantages and other advantages, and features of the
present description will be readily apparent from the following
Detailed Description when taken alone or in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages described herein will be more fully understood by
reading an example of an embodiment, referred to herein as the
Detailed Description, when taken alone or with reference to the
drawings, wherein:
FIG. 1 is a schematic diagram of an engine configured to operate
with heated fuel injectors;
FIG. 2 is a flowchart of an example fuel injector;
FIG. 3 is a schematic diagram of an example injector fuel heating
circuit;
FIG. 4 is a schematic diagram of another example injector fuel
heating circuit;
FIG. 5 is a schematic diagram of another example injector fuel
heating circuit;
FIG. 6 is a plot illustrating current control for fuel injector
fuel heating; and
FIG. 7 is a flow chart of an example fuel heating method.
DETAILED DESCRIPTION
Referring to FIG. 1, internal combustion engine 10, comprising a
plurality of cylinders, one cylinder of which is shown in FIG. 1,
is controlled by electronic engine controller 12. Engine 10
includes combustion chamber 30 and cylinder walls 32 with piston 36
positioned therein and connected to crankshaft 40. Combustion
chamber 30 is known communicating with intake manifold 44 and
exhaust manifold 48 via respective intake valve 52 and exhaust
valve 54. Intake manifold 44 is shown communicating with optional
electronic throttle 62.
Fuel is directly injected into combustion chamber 30 via fuel
injector 66. The fuel injector is an example of an electrically
operable mechanical valve. Fuel injector 66 receives opening and
closing signals from controller 12. Camshaft 130 is constructed
with at least one intake cam lobe profile and at least one exhaust
cam lobe profile. Alternatively, the intake cam may have more than
one lobe profile that may have different lift amounts, different
durations, and may be phased differently (i.e., the cam lobes may
vary in size and in orientation with respect to one another). In
yet another alternative, the system may utilize separate intake and
exhaust cams. Cam position sensor 150 provides cam position
information to controller 12. Intake valve rocker arm 56 and
exhaust valve rocker arm 57 transfer valve opening force from
camshaft 130 to the respective valve stems. Intake rocker arm 56
may include a lost motion member for selectively switching between
lower and higher lift cam lobe profiles, if desired. Alternatively,
different valvetrain actuators and designs may be used in place of
the design shown (e.g., pushrod instead of over-head cam,
electromechanical instead of hydro-mechanical).
Fuel is delivered to fuel injector 66 by a fuel system (not shown)
including a fuel tank, fuel pump, and fuel rail (not shown). Engine
10 may be designed to operate on one or more non-limiting fuel
types such as diesel, gasoline, alcohol, or propane.
A distributor-less ignition system (not shown) may provide ignition
spark to combustion chamber 30 via a spark plug (not shown) in
response to controller 12. Universal Exhaust Gas Oxygen (UEGO)
sensor 76 is shown coupled to exhaust manifold 48 upstream of
catalytic converter 70. Two-state exhaust gas oxygen sensor 98 is
shown coupled to exhaust pipe 49 downstream of catalytic converter
70. Converter 70 may include multiple catalyst bricks, particulate
filters, and/or exhaust gas trapping devices.
Controller 12 is shown in FIG. 1 as a conventional microcomputer
including: microprocessor unit 102, input/output ports 104,
read-only memory 106, random-access memory 108, keep-alive memory
110, and a conventional data bus. Controller 12 is shown receiving
various signals from sensors coupled to engine 10, in addition to
those signals previously discussed, including: engine coolant
temperature (ECT) from temperature sensor 112 coupled to cooling
sleeve 114; a position sensor 119 coupled to an accelerator pedal;
a measurement of engine manifold pressure (MAP) from pressure
sensor 122 coupled to intake manifold 44; engine knock sensor (not
shown); fuel type sensor (not shown); humidity from humidity sensor
38; a measurement (ACT) of engine air temperature or manifold
temperature from temperature sensor 117; and an engine position
sensor from a Hall effect sensor 118 sensing crankshaft 40
position. In a preferred aspect of the present description, engine
position sensor 118 produces a predetermined number of equally
spaced pulses every revolution of the crankshaft from which engine
speed (RPM) can be determined.
Controller 12 storage medium read-only memory 106 can be programmed
with computer readable data representing instructions executable by
processor 102 for performing the methods described below as well as
other variants that are anticipated but not specifically
listed.
Referring now to FIG. 2, a schematic of an example direct injection
fuel injector is shown. Fuel injector 200 is designed to inject
fuel directly into a cylinder of an internal combustion engine.
However, the present description is not restricted to direct
injectors or to injectors having the same design as the illustrated
injector. For example, the present description may be utilized on
port or central fuel injectors, or it may be used with fluid (e.g.,
oil) assisted intensifier injectors. FIG. 2 is not intended to
limit the scope or breadth of the present description.
Returning to FIG. 2, fuel is fed to the injector through port 201.
Pressurized liquid fuel occupies reservoirs 250 and 252 until
injected to a cylinder. Needle valve 232 regulates the flow of fuel
from the injector to the cylinder through nozzle 204. The needle
valve position is controlled by flowing electrical current through
coil 203. The electrical current passing through coil 203 induces a
magnetic field around coil 203 that attracts armature 209 toward
the coil. As armature 209 approaches coil 203, spring 221 is
compressed, and needle valve 232 lifts from the injector nozzle
seat. Fuel then flows to the cylinder.
Fuel in reservoirs 250 and 252 can be heated by passing current
through positive temperature coefficient (PTC) ceramic heating
elements 207 and 205. Alternatively, fuel may be heated using
negative temperature coefficient (NTC) heating elements if desired.
The heated fuel exits the fuel injector when the armature 209 is
attracted to coil 203.
Current flows to the injector from electrical connector 210 via two
electrical connector pins 211, one of which is shown. Heating
elements 205 and 207 along with actuator coil 203 are electrically
connected to pins 211. Diodes 233 and 231 (or similar current
direction controlling devices) are inserted in the electrical path
between electrical connector 210 and devices 203, 207, and 205.
Diodes 233 and 231 substantially limit the direction of current
through coil 203 and heating elements 207 and 205. That is, the
diodes permit substantially full current flow (i.e., current flow
is only reduced by a small voltage drop across the diode) in one
direction and limit current flow in the opposite direction to a few
milliamps. A few circuit examples are illustrated in FIGS. 3 and
4.
Referring now to FIG. 3, an example circuit for bi-directionally
controlling current to a fuel injector and heater is shown. Power
supply 301 provides current to actuate and heat fuel injector
components identified by region boundary 311. The direction of
current supplied to fuel injector 311 is determined by the state of
switches 303, 307, 305, and 309. Current flow can be initiated in a
first direction by closing switches 307 and 305. Current flow in a
second direction can be initiated by closing switches 303 and 309.
Switches may be of solid-state (e.g., transistors) or mechanical
construction (e.g., relays). Diodes 350, 352, 354, and 356 are
included to dissipate inductive energy when switches 303, 307, 305,
and 309 are operated.
Current flows through the fuel injector via pins 323 and 321. Note
that a unique feature over this design is the reduction in pin
count over other fuel heating injector designs. In this example,
pins 323 and 321 provide power to actuator coil 313 and heater
element 317. Operation of coil 313 and heater element 317 is
determined by the direction of current flow because diodes 315 and
319 are biased in different directions.
If current flows into fuel injector pin 327 from wiring harness pin
323, and out of fuel injector pin 325 and wiring harness pin 321,
then coil 313 can operate because diode 315 is forward biased. In
these conditions diode 319 is reverse biased and substantially
stops current flowing to heater element 317.
If on the other hand current flows from fuel injector pin 325 to
fuel injector pin 327, heating element 317 can heat fuel because
diode 319 is forward biased. Under this condition diode 315 is
reverse biased and substantially limits current flow to actuator
coil 313.
Thus, the circuit illustrated in FIG. 3 provides two separate
functions (actuating a fuel injector and heating fuel in the fuel
injector via heating elements) by way of a single electrical
connector and a single pair of electrical terminals. By simply
changing current direction, the fuel injector function is
completely changed. Further, the functions are virtually decoupled
from each other. That is, the illustrated circuit allows the fuel
injector to be actuated and inject fuel to a cylinder without
substantially heating fuel in the injector (when current flows to
coil 313 only a small amount of current dependant on the diode
design passes diode 319 (e.g., a few milliamps) reaches heating
element 317). Consequently, the present description provides for a
fuel injector that functions to inject fuel to a cylinder and heat
fuel in the injector by way of a heating element that is distinct
and separate from the actuator coil.
In addition, the illustrated circuit permits various levels of
current to be applied to the coil or heater without causing a
device to inadvertently operate. For example, 1 amp or 4 amps can
be applied to the heater without causing the coil to actuate the
fuel injector. This allows coil or heater operation to be adjusted
based on engine operating conditions if desired.
Referring now to FIG. 4, an alternative circuit for controlling
current to a fuel injector and heater is shown. Power supply 401,
switches 403, 407, 405, and 409 are used in the manner described in
FIG. 3 to control the direction of current flow into the fuel
injector components identified by boundary 411. Likewise similar to
FIG. 3, diodes 450, 452, 454, and 456 are included to dissipate
inductive energy when switches 403, 407, 405, and 409 are
operated.
If current flows into fuel injector pin 427 from wiring harness pin
423, and out of fuel injector pin 425 and wiring harness pin 421,
then coil 413 can operate because no diode blocks the current flow.
In these conditions diode 419 is reverse biased and substantially
stops current flowing to heater element 317.
If on the other hand current flows from fuel injector pin 425 to
fuel injector pin 427, heating element 417 can heat fuel because
diode 419 is forward biased. In one embodiment during these
conditions, current flowing into the injector can be kept below a
predetermined level at which the fuel injector actuates and injects
fuel. This allows the heater to operate without actuating the fuel
injector. Alternatively, if desired, current can be increased to a
predetermined level at which the fuel injector is actuated and
heater temperature increases.
Thus, this circuit configuration allows the fuel injector to be
operated independent of heater operation, or alternatively, it
allows the heater to be operated while the injector is actuated.
Further, when the level of current is controlled, this circuit
permits the fuel injector to heat fuel in the fuel injector without
actuating the fuel injector.
Referring now to FIG. 5, an example of a fuel heating circuitry
integrated into an engine controller is illustrated. Engine
controller 12 is comprised of a bank of high-side drivers 505,
low-side drivers 507, and a relay control switch (e.g., a
transistor) 511. External relay 503 is toggled between a first
(lower potential) and second (higher potential) voltage depending
on the state of relay control switch 511. Alternatively, the
external relay 503 may be substituted with solid-state circuitry,
if desired.
Circuitry of four heated fuel injectors is within boundary region
501. This injector circuitry represents an example of circuitry for
heating fuel for a four cylinder engine. Cylinder number one fuel
injector circuitry is within boundary region 520, while fuel
injectors for cylinders two through four are shown in boundary
regions 522, 524, and 526 respectively.
Relay 503 is shown connecting fuel injectors 520, 522, 524, and 526
to a first voltage reference. Relay 503 may also connect the same
fuel injectors to a second voltage reference V+. The second voltage
reference is at a higher potential than the first voltage
reference. The operating state of switch 511 determines whether
relay 503 connects fuel injectors 520, 522, 524, and 526 to the
first or second voltage reference.
High-side driver 505 is comprised of individual solid-state
switches that are connected to the second voltage reference on one
side of the switches and to fuel injectors 520, 522, 524, and 526
on the other side of the switches.
Low-side driver 507 is also comprised of individual solid-state
switches that are connected to the first voltage reference on one
side of the switches and to fuel injectors 520, 522, 524, and 526
on the other side of the switch.
Fuel is heated in the injector by controlling relay control switch
511 and high-side driver 505. Specifically, relay control switch
511 is set to a state whereby control relay 503 connects the first
voltage reference to a terminal of fuel injectors 520, 522, 524,
and 526. In addition, switches internal to high-side injector 505
are closed such that the second voltage reference is routed to a
second terminal of fuel injectors 520, 522, 524, and 526. Current
then flows from the second voltage reference to the first voltage
reference in a direction that forward biases a diode in an
electrical path going to the heating element of each fuel
injector.
On the other hand, the fuel injector is actuated by controlling
relay control switch 511 and low-side driver 507. Specifically,
relay control switch 511 is set to a state whereby control relay
503 connects the second voltage reference to a terminal of fuel
injectors 520, 522, 524, and 526. And, switches internal to
low-side injector 507 are closed such that the second voltage
reference is routed to a second terminal of fuel injectors 520,
522, 524, and 526. Current then flows from the second voltage
reference to the first voltage reference in a direction that
reverse biases a diode in an electrical path going to the heating
element of each fuel injector. In this way, current is allowed to
flow through the injector actuator coils but is limited or blocked
from passing through the injector heating element. Thus, current
can be driven in one direction to actuated the fuel injector and in
a different direction to heat fuel in the injector.
It should be noted that when current is driven in a direction that
forward biases the diodes illustrated in FIG. 5, the level of
current can be restricted or regulated by high-side driver 505 such
that the fuel injector is not actuated.
FIG. 6 is plot of example current supplied to fuel injectors of a
four-cylinder engine. Signals INJ1-4 represent current delivered to
fuel injectors. The "+" represents current being driven into a fuel
injector in a second direction. The "-" represents current being
driven into the fuel injector in a first direction, opposite the
second direction. The location that is approximately half way
between the "+" and "-" represents substantially no current flowing
into the fuel injector.
Engine position relative to top-dead-center compression stroke of
cylinder number one is represented by the signal labeled CRK.
Engine cranking and starting begins at vertical marker 601 and the
sequence flows from left to right.
Note that the current illustrated in FIG. 6 is not necessarily
indicative of the actual current profile. Current is illustrated in
FIG. 6 to show an example of when fuel heating may be accomplished
relative to fuel injector actuation, the illustration is not meant
to illustrate an actual current profile. Also note that fuel
heating time may vary from that illustrated without deviating from
the scope or breadth of the description. For example, the injector
opening timing illustrated at 605 may be increased or decreased or
changed with respect to engine position. Further, the amount of
current used to open the fuel injector may be increase above the
amount of current necessary to open the fuel injector. The
resulting additional current can be transformed into heat to
further heat the fuel within the injector. Likewise, fuel heating
intervals may also vary from those illustrated. For example,
between injections at 605 and 619 the heater is shown as being on
for the entire interval. However, if desired, the fuel heating may
take place for only a fraction of the interval. Furthermore, only a
few engine cycles are shown whereas fuel heating may go on for a
predetermined period of time or for a specific number of cylinder
cycles that exceeds the number illustrated.
Also note that the present method is capable of heating fuel over
the engine operating range if desired. For example, fuel heating
can be used during a start as well as during engine operation.
Heating fuel during engine operation allows the present method to
control the cylinder charge temperature.
At 603, current is directed into fuel injector number one in the
first direction. This begins heating fuel in the fuel injector.
Current flow ceases briefly in region 604. As the engine begins to
rotate, right of vertical marker 601, the first injector actuation
command is issued at 605. This command directs current into the
fuel injector in a second direction. Fuel heating resumes in region
606 when current to fuel injector number one is resumed in the
first direction. Fuel is injected to cylinder number one again when
current is reversed and sent into fuel injector number one at 619.
The described sequence for heating and injecting fuel at fuel
injector number one continues until heating is stopped in region
621.
Fuel injector number two follows a similar sequence as fuel
injector number one, but fuel heating begins at region 607, the
first injection occurs at 609 and fuel heating is stopped at 623.
The initial fuel heating at 607 is offset in time from the fuel
heating in injector one at 603. This reduces the instantaneous
current draw from the vehicle power source before the engine is
started. If the vehicle power source has sufficient capacity, fuel
in all fuel injectors may be simultaneously heated. In still
another embodiment, fuel may be heated at different times in
selected groups of fuel injectors. Current at 611 and 615
represents initial fuel heating for cylinders three and four. Fuel
injector current at 613 and 617 represents initial actuation
current. Fuel injector current at 625 and 627 is substantially zero
between injector openings because cylinder temperature has
increased to a level that promotes fuel vaporization.
Referring now to FIG. 7, a flow chart of an example fuel injector
heating method is shown.
Note that in at least one embodiment, current to actuate a fuel
injector (actuation current) enters the fuel injector through an
electrical connector having two pins and is delivered in a second
direction. Current to heat fuel flowing through the fuel injector
is delivered through the same electrical connector and pins but in
a first direction, opposite to the second direction described to
actuate the fuel injector.
In step 701, the routine determines if fuel heating has been
requested. A request for fuel heating may come from an external
routine or it may result from evaluating the state of sensors and
systems. In one example, the states of engine temperature, time
since last engine start, oil temperature, desired cylinder charge
temperature, and fuel temperature are used to determine if fuel
heating is desired. Further, operating conditions can be used to
determine the duration of fuel heating. In one example, the fuel
heating duration may be determined by retrieving empirically
determined heating times from memory. Specific memory locations may
be interrogated by indexing arrays that are organized by engine
coolant temperature and engine oil temperature, for example.
In step 703, the fuel injector heating delivery mode is selected.
The heating mode describes how and when the fuel heating is
delivered to one or more fuel injectors. For example, during an
engine start, heat may be delivered to fuel through a group of
injectors in a sequential manner and the amount of heat delivered
by each injector can be varied in response to operating
conditions.
In one embodiment, fuel heat delivery mode can be split into two
regions. Specifically, the time before the engine is started and
the time after the engine is started. Heat may be delivered to the
fuel through a fuel injector before a start in a way that may be
different from the way that heat is added to fuel after a start.
For example, before the engine begins to rotate the heating
sequence may be based on time. That is, current can be sent to heat
a different individual injector every 2 seconds, for example. After
the engine is started, heat may be delivered at predetermined
crankshaft intervals for a predetermined time or crankshaft
angle.
Fuel heating by the fuel injector may be delivered to the injectors
simultaneously; to groups of injectors where the injectors of a
group are simultaneously heated, and where the injector groups are
heated at different times; sequentially to all or a group of
injectors; or in combinations of the before-mentioned ways. In one
embodiment, current is supplied to two or more fuel injectors
simultaneously. That is, current for injector heating the injectors
is delivered at substantially the same time. Alternatively, it is
also possible to deliver current to heat the injectors
sequentially. For example, current for injector heating can be
supplied to a first injector, stopped, supplied to a second
injector, stopped, and continued in the same manner to the
remaining injectors.
In addition, this sequence may be repeated until operating
conditions, such as time since key-on has reached a predetermined
level or until engine oil temperature reaches a desired level, for
example. As mentioned above, after the engine is started, the fuel
injector heating may be continued or may be stopped. Further, the
amount of heat transferred when the engine is stopped may be
different from the amount of heat delivered after the engine is
started.
Engine operating conditions (e.g., engine temperature, fuel
temperature, cylinder charge temperature, barometric pressure) may
be used to determine when to deactivate injector heating. In
addition, the fuel heating mode and the timing when heat is
delivered to the fuel may also be varied as the engine begins to
rotate.
FIG. 6 shows one example of a fuel injector heating delivery mode
that is available from the present description. Specifically,
injector heating is delivered at predetermined crankshaft intervals
so that the heating does not interfere with injector operation.
Further, it is also possible to briefly deactivate heating to one
injector if current is needed to actuate another fuel injector
during the same crankshaft interval. For example, if fuel injector
heating is scheduled for cylinder number four fuel injector between
540 and 0 crankshaft degrees referenced to top-dead-center of
cylinder one, and fuel injection is scheduled for cylinder number
one during this same interval, then the heating for cylinder four
fuel injector may be deactivated while injection commands are
issued to the cylinder number one fuel injector.
Continuing with step 703, the heating mode may be determined by
assessing engine operating conditions, injector operating
conditions including barometric pressure, humidity, cylinder charge
temperature, and engine temperature. In one embodiment, the
operating conditions may be used to exercise a state machine that
can activate different heat delivery modes before and after
starting. The selection of these heat delivery modes may be
empirically determined, for example. FIG. 6 provides a sample of
the available heating modes that may be selected. The routine
proceeds to step 705 after the heat delivery mode is selected.
Referring now to step 705, the fuel is heated in the injectors. In
one embodiment, the fuel heating duration may be reduced or
increased based on the type of fuel being heated. Specifically, in
one example, a sensor can determine the concentration ethanol in a
fuel line leading to the fuel injector. The fuel heating time can
be varied as the concentration of ethanol increases in the fuel
line. In addition, the rate that heat is delivered to the fuel can
be varied as the fuel type varies (e.g., as the concentration of
ethanol varies) by varying the amount of current supplied to the
heating element. Further, the rate heat is transferred and/or the
duration of fuel heating can be varied as the engine's or vehicle's
altitude varies. Further still, the rate heat is transferred and/or
the duration of fuel heating can be varied as the ambient air
humidity varies and/or as engine temperature varies.
In one embodiment, the heating duration and heat transfer rate are
empirically determined and stored in engine controller memory for
later retrieval and use. In one embodiment, the amount of fuel
heating is reduced as barometric pressure is reduced (i.e.,
altitude increases).
As noted above, the present method can also adjust fuel temperature
to affect the cylinder charge temperature. In one embodiment,
desired cylinder charge temperature is mapped over the engine
operating ranges for a particular type of fuel (e.g., ethanol). A
model infers cylinder charge temperature from intake air
temperature, engine temperature, engine speed, cylinder air charge
amount, fuel type, and injection timing. If the inferred cylinder
charge temperature deviates from the desired cylinder charge
temperature, then heat can be added to the fuel (i.e., the rate of
heat addition and/or the amount of time heat is delivered to fuel)
or the heater can be deactivated so that the desired temperature is
reached.
Thus, the present method is capable of adjusting the rate of heat
transfer from a fuel injector to fuel, as well as the fuel heating
duration in response to environmental and vehicle operating
conditions.
In one example, the amount of heat transferred over a period of
time to the fuel delivered to the engine after the engine is
started may be increased as compared to the amount of heat
delivered to fuel before the engine is started. The present method
also allows different heat transfer rates to the fuel depending on
the power source. When the power to heat fuel comes from a battery,
current may be a first amount. When power to heat fuel comes from
an alternator, current may be a second amount, different from the
first amount.
As previously mentioned, the fuel may be heated by PTC or NTC
devices. Further, the actuator coil may be used to heat the fuel as
well. The PTC/NTC heating elements may transfer heat directly to
fuel or they may transfer heat to fuel through an intermediate
material by conduction. Similarly, the actuator coil may transfer
heat to fuel by using the internal resistance of the fuel injector
coil to heat the injector components that surround the coil. The
coil heat can be transferred to the surrounding material through
conduction. The coil resistance transforms the electrical energy
entering the coil into thermal energy. By applying a controlled
current to the fuel injector coil, the temperature of the injector
coil may be regulated so that the coil transfers a desired amount
of thermal energy to the surrounding injector while maintaining the
temperature of the coil below a predetermined level. In one
example, current supplied to the coil is regulated below a
predetermined amount so that there is insufficient current to
operate the injector, but enough to heat fuel within the
injector.
In addition, eddy current heating may also be used to heat fuel by
generating a time-varying magnetic field from varying the current
that flows into the actuator coil. The current may be varied in a
variety of ways. For example, the current entering the coil may be
increased and decreased over a specified time interval, or if the
engine is rotating, the current may be increased or decreased over
a specified crankshaft interval (e.g., The excitation frequency may
be adjusted by a predetermined amount every 3600 crankshaft angle
degrees. As the current varies, a magnetic field external to the
coil varies and ferrous material in the field resists the changing
magnetic field, thereby heating the ferrous material. Heat is
conducted from the ferrous material to the fuel.
The current flow to the fuel injector may be controlled by an H
bridge that allows bi-directional current flow, or by other
circuitry that provides a similar function.
Also note that the fuel injection timing may be adjusted as a
function of the time fuel injectors are heated or as the amount of
heating energy supplied to a fuel injector varies. For example, at
a constant engine speed and load, the fuel injection pulse-width
may be decreased as the amount of heat energy supplied to a fuel
injector increases. This feature allows an engine controller to
compensate for the improved response of a heated injector. After
the coils start to heat, the routine proceeds to step 707.
In step 707, the routine determines whether or not the engine is
ready to start after fuel heating has commenced. In one embodiment,
if the fuel has reached a desired temperature or a time since
key-on, the engine controller 12 can notify the operator that the
engine is ready to start or the engine may be started in other
circumstances. In other embodiments, the engine may be considered
ready to start after a desired amount of heating energy has been
supplied to fuel in one or more injectors. For example, the engine
may be considered ready to start if a predetermined number of
joules of energy have been dissipated by each fuel injector heating
element. Also note that in some embodiments, the engine may be
allowed to start as soon as instructed by an operator. That is,
fuel heating may be initiated but the engine may be started whether
or not fuel has reached a desired temperature. If this mode of
operation is selected, the fuel pulse-width may be adjusted to
improve starting. If the routine determines that the engine is
ready to start the routine proceeds to step 711. Otherwise, the
routine returns to step 705.
In step 711, the injectors are controlled so that the desired
amount of fuel is injected to the cylinders at the desired timing.
That is, current is delivered in a second direction such that it
flows through the actuator coil substantially unencumbered (e.g., a
small reduction in current caused by a voltage drop across a diode
or similar device is anticipated and permissible). When current is
directed in this manner, the fuel injectors are operated in a way
that is similar to conditions when injector heating is not desired.
That is, current is supplied to the injector at a crankshaft angle
and desired duration that delivers the desired amount of fuel to
the cylinder.
In step 713, the routine determines if fuel heating is desired
while the engine is operating. If it is, the routine proceeds to
step 715. If not, the routine proceeds to exit. If no fuel heating
is desired during engine operation, current flow is limited to the
second direction, and the injectors are operated by the main fuel
injection routine and fuel is delivered in response the engine
speed, operator demand, and operating conditions.
In step 715, the fuel is heated by applying current to the fuel
injector in a first direction while the injector is not actuated.
That is, as described above, when current flows to the fuel
injector in a second direction the injector is actuated. Current
flows to the fuel injector in a first direction, different from the
second direction, to heat fuel passing through the injector.
Accordingly, current is repeatedly reversed as the engine operates.
For example, current flows into the coil when it is delivered to
the injector in a second direction. When the injector has delivered
the desired amount of fuel, the current is reversed and delivered
in a first direction to heat fuel passing through the injector. The
heating current may be delivered to the fuel injector for the
entire period between fuel injections, or it may be delivered for a
fraction of the period between injections.
The rate of heat delivery to the fuel and the duration heat is
transferred to the fuel can be an open-loop or closed-loop control
process. In one embodiment, fuel heating rate and duration are
determined after assessing engine temperature, barometric pressure,
and humidity. In this example, fuel heating follows a prescribed
schedule that has been programmed into the engine controller.
In a closed-loop embodiment, engine sensors are repeatedly
monitored and used to determine operating conditions so that the
heat transfer rate and duration of fuel heating can be revised as
engine operating conditions vary. Specifically, the following
calculations are one example method to determine the heat transfer
rate.
HeatCur=Basecur(N)curh(hum)curftem(fueltemp)curetem(engtemp)curftyp(ftype-
)curbar(baro) Where HeatCur is the amount of current to deliver in
a heating interval, where Basecur is an empirically determined base
amount of current that is a function of engine speed N, where curh
is a modifier that is a function of humidity hum, where curftem is
a modifier that is a function of fuel temperature fueltemp, where
curetemp is a modifier that is a function of engine temperature
engtemp, where curftype is a modifier that is a function of fuel
type ftype, and where curbar is a modifier that is a function of
barometric pressure baro.
The fuel heating duration can be determined from a similar
function.
DurCur=Basedurdurh(hum)durftem(fueltemp)duretem(engtemp)durftyp(ftype)dur-
bar(baro) Where DurCur is the duration current is delivered, where
Basedur is an empirically determined base duration of current,
where durh is a modifier that is a function of humidity hum, where
durftem is a modifier that is a function of fuel temperature
fueltemp, where duretemp is a modifier that is a function of engine
temperature engtemp, where durftype is a modifier that is a
function of fuel type ftype, and where durbar is a modifier that is
a function of barometric pressure baro.
Note as mentioned above, current control can vary depending on the
circuitry within the fuel injector. For example, if current is
impeded in one direction through the PTC/NTC heating element, and
current is not impeded through the actuator coil, it may be
desirable to limit current flow to the entire fuel injector
(actuator coil and heating element) so that the fuel injector does
not actuate when fuel is being heated. On the other hand, if
current flow can be impeded through both the actuator coil and the
heating element, heating current may not have to be limited to as
low of a level as if current where flowing through both the
actuator coil and the heating element.
While the engine is being operated, it is desirable to keep the
fuel injectors delivering a commanded amount of fuel. This can be
accomplished by heating the injector during the portion of a
cylinder cycle where fuel is not injected. For example, the fuel
injectors may be heated during the power or exhaust strokes. FIG. 6
shows an example of heating the fuel injectors while the engine is
operating. Of course, the fuel injector heating interval may be
varied from that which is shown in FIG. 6, if desired. One
convenient way to achieve heating during engine operating is to
time the heating period with engine positions. That is, the heating
interval can be between bottom-dead-center of the exhaust stroke
and top-dead-center of the exhaust stroke of the cylinder
associated with the injector being heated, for example. After the
coil current sequences are determined and commanded the routine
returns to step 711.
This concludes the description. The reading of it by those skilled
in the art would bring to mind many alterations and modifications
without departing from the spirit and the scope of the description.
For example, I3, I4, I5, V6, V8, V10, V12, and turbine engines
operating on non-limiting fuel types such as ethanol, kerosene, jet
fuel, gasoline, propane, proponol, diesel, or other alternative
fuel configurations could use the present description to
advantage.
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